linux-kernel - Re: [RFC] arm64: Ensure proper addressing for ldnp/stnp

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Date:   Mon, 19 Sep 2016 14:41:10 -0400
From:   bdegraaf@...eaurora.org
To:     Laura Abbott <labbott@...hat.com>
Cc:     catalin.marinas@....com, will.deacon@....com, james.morse@....com,
        mark.rutland@....com, andre.przywara@....com,
        jungseoklee85@...il.com, apinski@...ium.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        timur@...eaurora.org, cov@...eaurora.org
Subject: Re: [RFC] arm64: Ensure proper addressing for ldnp/stnp

On 2016-09-19 14:28, Laura Abbott wrote:
> On 09/19/2016 10:36 AM, Brent DeGraaf wrote:
>> According to section 6.3.8 of the ARM Programmer's Guide, non-temporal
>> loads and stores do not verify that address dependency is met between 
>> a
>> load of an address to a register and a subsequent non-temporal load or
>> store using that address on the executing PE. Therefore, context 
>> switch
>> code and subroutine calls that use non-temporally accessed addresses 
>> as
>> parameters that might depend on a load of an address into an argument
>> register must ensure that ordering requirements are met by introducing
>> a barrier prior to the successive non-temporal access.  Add 
>> appropriate
>> barriers whereever this specific situation comes into play.
>> 
> 
> Was this found by code inspection or is there a (public) exciting test
> case to observe this behavior?
> 
> Thanks,
> Laura
> 

Code inspection only.

Brent